全新java初学者实践教程6(Java SE5.0版)
\ p3v#0R{ 基本语法3
l/M[am 5E`JD ZEqE$: 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
J)#S-ZB+'k ac|/Y$\w [font="Times] 1.循环语句[font="Times]:while,do-while,for
.wD>Gs{sH[ 4j^bpfb, [font="Times]2.分支语句[font="Times]:if-else,switch,
l:)S 3 [font="Times]
bfhz?,b 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
x df?nt [font="Times]
7x(v? 4.异常处理语句[font="Times]:try-catch-finally,throw
.D!WO w]}f6VlEl 实践:
^(DL+r, [font="Times] 1.循环语句
6(>WGR [font="Times] while 语句
k&!6fZ) [font="Times]class While {
$7Cgo &J [font="Times]public static void main(String args[]) {
{U^j&E [font="Times]int n = 10;
<W2ZoqaV [font="Times]while(n > 0) {
xdqK.Z% [font="Times]System.out.println("tick " + n);
7C?E z%a@ [font="Times]n--;
Tv1]v. [font="Times]}
;5N41_hG [font="Times]}
^;4YZwW5w [font="Times]}
a5)JkC [font="Times] do…while 语句
1U'ZVJ5bpK [font="Times] class DoWhile {
fq=:h\\G [font="Times]public static void main(String args[]) {
\qB6TiB/ [font="Times]int n = 10;
>P<'L4; [font="Times]do {
W6i3Psjsw [font="Times]System.out.println("tick " + n);
qW3x{L$c [font="Times]n--;
m2Q$+p@ [font="Times]} while(n > 0);
i\ "{# [font="Times]}
:Pf>Z? /d [font="Times]}
WI{ ;#A 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
&y\igX1 [font="Times] for语句
f]]f85 [font="Times] class ForTick {
L0xsazX:x [font="Times]public static void main(String args[]) {
9OfU7_m [font="Times]int n;
9>;} /*:H [font="Times]for(n=10; n>0; n--)
ZL,8,;] [font="Times]System.out.println("tick " + n);
[1U{ci&=p [font="Times]}
"O``7HA} [font="Times]}
v1h.pbz`w 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
DL1
+c`d 还有啊,[font="Times]for循环的部分可以为空的
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[font="Times]class ForVar {
;P8(Zf3wJb [font="Times]public static void main(String args[]) {
~2(]ZfO?>H [font="Times]int i;
]);NnsG [font="Times]boolean done = false;
^obC4( [font="Times]i = 0;
; [FLT:$ [font="Times]for( ; !done; ) {
op.d;lO@ [font="Times]System.out.println("i is " + i);
ly=a>}F_ [font="Times]if(i == 10) done = true;
H#`8Ey [font="Times]i++;
#N$9u"8C [font="Times]}
c;^A)_/ [font="Times]}
(-J<Vy] [font="Times]}
循环语句的例子下载 R+uw/LG [font="Times] 2.分支语句[font="Times]
;?`@"YG) [font="Times] if/else语句
%4/xH9 [font="Times]class IfElse {
JRo;(wqZ [font="Times]public static void main(String args[]) {
Bq;1^gtpe [font="Times]int month = 4; // April
x9D/s`! [font="Times]String season;
d#8e~ [font="Times]if(month == 12 || month == 1 || month == 2)
.:N:p We [font="Times]season = "Winter";
FB_NkXR [font="Times]else if(month == 3 || month == 4 || month == 5)
dXK-&Po' [font="Times]season = "Spring";
@h9K [font="Times]else if(month == 6 || month == 7 || month == 8)
d>/Tu_ y [font="Times]season = "Summer";
TL'0T,Jo [font="Times]else if(month == 9 || month == 10 || month == 11)
}/"4|U [font="Times]season = "Autumn";
%/!+(7
D [font="Times]else
<]'|$8&jY [font="Times]season = "Bogus Month";
MyFCJJ/ [font="Times]System.out.println("April is in the " + season + ".");
_ Mn6 L= [font="Times]}
wPgDy [font="Times]}
SiR\a!, C [font="Times]//这段程序输出[font="Times]:
h1-Gp3# [font="Times]//April is in the Spring.
p#=;)1 [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
f"P$f8$ [font="Times] switch语句
_A3X6 [font="Times] class Switch {
@ZG>mP1Vo [font="Times]public static void main(String args[]) {
c=aO5(i0 [font="Times]int month = 4;
yV2e5/i [font="Times]String season;
^vaL8+ [font="Times]switch (month) {
5k~\or 5_ [font="Times]case 12:
m9!DOL1pl [font="Times]case 1:
_r5wF(Y?7 [font="Times]case 2:
7>mhK7l [font="Times]season = "Winter";
Wc\+x1 :8 [font="Times]break;
ZB0+GG\ [font="Times]case 3:
S<pkc8 [font="Times]case 4:
2vvh|?M [font="Times]case 5:
C`EY5"N r [font="Times]season = "Spring";
GW8CaTf~ [font="Times]break;
2LZS|fB9o [font="Times]case 6:
MQ9vPgh [font="Times]case 7:
Qi^;1& [font="Times]case 8:
NWaO_sm [font="Times]season = "Summer";
sv`"\3N[ [font="Times]break;
dN0mYlu1| [font="Times]case 9:
.)t(:)*b [font="Times]case 10:
{2EMz|&8 [font="Times]case 11:
o3\,gzJ [font="Times]season = "Autumn";
n.ct]+L [font="Times]break;
Z/h|\SyJ [font="Times]default:
y!hi"! [font="Times]season = "Bogus Month";
~#4~_d.=L [font="Times]}
OfJd/D [font="Times]System.out.println("April is in the " + season + ".");
jzMg'z/@J [font="Times]}
`)2[ST [font="Times]}
分支语句代码下载 oLw|uU-| gmDR{loX [font="Times]switch语句适合于条件非常多的逻辑
h1c{?xH2r 请看上述语句可以混合使用,请看
下载例子